Digitally controlled driver for lighting fixture

ABSTRACT

The present disclosure relates to a lighting fixture that is capable of providing white light over an extended range of correlated color temperatures.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to concurrently filed U.S. patentapplication Ser. No. ______ entitled LIGHTING FIXTURE PROVIDING VARIABLECCT and concurrently filed U.S. patent application Ser. No. ______entitled WALL CONTROLLER CONTROLLING CCT, the disclosures of which areincorporated herein by reference in their entireties.

FIELD OF THE DISCLOSURE

The present disclosure relates to lighting fixtures and controlstherefor, and in particular to controlling the color temperature oflighting fixtures.

BACKGROUND

In recent years, a movement has gained traction to replace incandescentlight bulbs with lighting fixtures that employ more efficient lightingtechnologies as well as to replace relatively efficient fluorescentlighting fixtures with lighting technologies that produce a morepleasing, natural light. One such technology that shows tremendouspromise employs light emitting diodes (LEDs). Compared with incandescentbulbs, LED-based light fixtures are much more efficient at convertingelectrical energy into light, are longer lasting, and are also capableof producing light that is very natural. Compared with fluorescentlighting, LED-based fixtures are also very efficient, but are capable ofproducing light that is much more natural and more capable of accuratelyrendering colors. As a result, lighting fixtures that employ LEDtechnologies are replacing incandescent and fluorescent bulbs inresidential, commercial, and industrial applications.

Unlike incandescent bulbs that operate by subjecting a filament to adesired current, LED-based lighting fixtures require electronics todrive one or more LEDs. The electronics generally include a power supplyand special control circuitry to provide uniquely configured signalsthat are required to drive the one or more LEDs in a desired fashion.The presence of the control circuitry adds a potentially significantlevel of intelligence to the lighting fixtures that can be leveraged toemploy various types of lighting control. Such lighting control may bebased on various environmental conditions, such as ambient light,occupancy, temperature, and the like.

SUMMARY

The present disclosure relates to a lighting fixture that is capable ofproviding white light over an extended range of correlated colortemperatures. In one embodiment, the lighting fixture includes a drivermodule and a number of LED strings. Each of the LED strings emits lightat a different color point. The driver module may be configured to:

-   -   store a current model for each string, wherein each current        model effectively defines current as a function of CCT over a        CCT range;    -   determine a desired CCT; and    -   generate a current for each string based on the desired CCT        using the corresponding current model.

As such, the light from each string mixes to form white light with acolor point that falls along a black body locus at the desired CCT.

Those skilled in the art will appreciate the scope of the disclosure andrealize additional aspects thereof after reading the following detaileddescription in association with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings incorporated in and forming a part of thisspecification illustrate several aspects of the disclosure, and togetherwith the description serve to explain the principles of the disclosure.

FIG. 1 is a perspective view of a troffer-based lighting fixtureaccording to one embodiment of the disclosure.

FIG. 2 is a cross section of the lighting fixture of FIG. 1.

FIG. 3 is a cross section of the lighting fixture of FIG. 1 illustratinghow light emanates from the LEDs of the lighting fixture and isreflected out through lenses of the lighting fixture.

FIG. 4 illustrates a driver module and a communications moduleintegrated within an electronics housing of the lighting fixture of FIG.1.

FIG. 5 illustrates a driver module provided in an electronics housing ofthe lighting fixture of FIG. 1 and a communications module in anassociated housing coupled to the exterior of the electronics housingaccording to one embodiment of the disclosure.

FIGS. 6A and 6B respectively illustrate a communications moduleaccording to one embodiment, before and after being attached to thehousing of the lighting fixture.

FIG. 7 illustrates a sensor module installed in a heatsink of a lightingfixture according to one embodiment of the disclosure.

FIG. 8A illustrates a sensor module according to one embodiment of thedisclosure.

FIG. 8B is an exploded view of the sensor module of FIG. 8A.

FIG. 9 is a block diagram of a lighting system according to oneembodiment of the disclosure.

FIG. 10 is a block diagram of a communications module according to oneembodiment of the disclosure.

FIG. 11 is a cross section of an exemplary LED according to a firstembodiment of the disclosure.

FIG. 12 is a cross section of an exemplary LED according to a secondembodiment of the disclosure.

FIG. 13 is CIE 1976 chromaticity diagram that illustrates the colorpoints for three different LEDs and a black body locus.

FIG. 14 is a schematic of a driver module and an LED array according toone embodiment of the disclosure.

FIG. 15 illustrates a functional schematic of the driver module of FIG.14.

FIG. 16 is a flow diagram that illustrates the functionality of thedriver module according to one embodiment.

FIG. 17 is a graph that plots individual LED current versus CCT foroverall light output according to one embodiment.

FIG. 18 is a wall controller for controlling one or more lightingfixtures according to a first embodiment.

FIG. 19 is a wall controller for controlling one or more lightingfixtures according to a second embodiment.

FIG. 20 is a wall controller for controlling one or more lightingfixtures according to a third embodiment.

FIG. 21 is a wall controller for controlling one or more lightingfixtures according to a fourth embodiment.

FIG. 22 is a wall controller for controlling one or more lightingfixtures according to a fifth embodiment.

FIG. 23 is a schematic for a wall controller according to oneembodiment.

FIGS. 24 and 25 are different isometric views of an exemplarycommissioning tool, according to one embodiment.

FIG. 26 is a block diagram of the electronics for a commissioning tool,according to one embodiment.

DETAILED DESCRIPTION

The embodiments set forth below represent the necessary information toenable those skilled in the art to practice the disclosure andillustrate the best mode of practicing the disclosure. Upon reading thefollowing description in light of the accompanying drawings, thoseskilled in the art will understand the concepts of the disclosure andwill recognize applications of these concepts not particularly addressedherein. It should be understood that these concepts and applicationsfall within the scope of the disclosure and the accompanying claims.

It will be understood that relative terms such as “front,” “forward,”“rear,” “below,” “above,” “upper,” “lower,” “horizontal,” or “vertical”may be used herein to describe a relationship of one element, layer orregion to another element, layer or region as illustrated in thefigures. It will be understood that these terms are intended toencompass different orientations of the device in addition to theorientation depicted in the figures.

The present disclosure relates to a lighting fixture that is capable ofproviding white light over an extended range of correlated colortemperatures. In one embodiment, the lighting fixture includes a drivermodule and a number of LED strings. Each of the LED strings emits lightat a different color point. The driver module may be configured to:

-   -   store a current model for each string, wherein each current        model effectively defines current as a function of CCT over a        CCT range;    -   determine a desired CCT; and    -   generate a current for each string based on the desired CCT        using the corresponding current model.

As such, the light from each string mixes to form white light with acolor point that falls along a black body locus at the desired CCT.

Prior to delving into the details of the present disclosure, an overviewof an exemplary lighting fixture is provided. While the concepts of thepresent disclosure may be employed in any type of lighting system, theimmediately following description describes these concepts in atroffer-type lighting fixture, such as the lighting fixture 10illustrated in FIGS. 1-3. This particular lighting fixture issubstantially similar to the CR and CS series of troffer-type lightingfixtures that are manufactured by Cree, Inc. of Durham, N.C.

While the disclosed lighting fixture 10 employs an indirect lightingconfiguration wherein light is initially emitted upward from a lightsource and then reflected downward, direct lighting configurations mayalso take advantage of the concepts of the present disclosure. Inaddition to troffer-type lighting fixtures, the concepts of the presentdisclosure may also be employed in recessed lighting configurations,wall mount lighting configurations, outdoor lighting configurations, andthe like. Reference is made to co-pending and co-assigned U.S. patentapplication Ser. No. 13/589,899 filed Aug. 20, 2013, Ser. No. 13/649,531filed Oct. 11, 2012, and Ser. No. 13/606,713 filed Sep. 7, 2012, thecontents of which are incorporated herein by reference in theirentireties. Further, the functionality and control techniques describedbelow may be used to control different types of lighting fixtures, aswell as different groups of the same or different types of lightingfixtures at the same time.

In general, troffer-type lighting fixtures, such as the lighting fixture10, are designed to mount in, on, or from a ceiling. In mostapplications, the troffer-type lighting fixtures are mounted into a dropceiling (not shown) of a commercial, educational, or governmentalfacility. As illustrated in FIGS. 1-3, the lighting fixture 10 includesa square or rectangular outer frame 12. In the central portion of thelighting fixture 10 are two rectangular lenses 14, which are generallytransparent, translucent, or opaque. Reflectors 16 extend from the outerframe 12 to the outer edges of the lenses 14. The lenses 14 effectivelyextend between the innermost portions of the reflectors 16 to anelongated heatsink 18, which functions to join the two inside edges ofthe lenses 14.

Turning now to FIGS. 2 and 3 in particular, the back side of theheatsink 18 provides a mounting structure for an LED array 20, whichincludes one or more rows of individual LEDs mounted on an appropriatesubstrate. The LEDs are oriented to primarily emit light upwards towarda concave cover 22. The volume bounded by the cover 22, the lenses 14,and the back of the heatsink 18 provides a mixing chamber 24. As such,light will emanate upwards from the LEDs of the LED array 20 toward thecover 22 and will be reflected downward through the respective lenses14, as illustrated in FIG. 3. Notably, not all light rays emitted fromthe LEDs will reflect directly off of the bottom of the cover 22 andback through a particular lens 14 with a single reflection. Many of thelight rays will bounce around within the mixing chamber 24 andeffectively mix with other light rays, such that a desirably uniformlight is emitted through the respective lenses 14.

Those skilled in the art will recognize that the type of lenses 14, thetype of LEDs, the shape of the cover 22, and any coating on the bottomside of the cover 22, among many other variables, will affect thequantity and quality of light emitted by the lighting fixture 10. Aswill be discussed in greater detail below, the LED array 20 may includeLEDs of different colors, wherein the light emitted from the variousLEDs mixes together to form a white light having a desired colortemperature and quality based on the design parameters for theparticular embodiment.

As is apparent from FIGS. 2 and 3, the elongated fins of the heatsink 18may be visible from the bottom of the lighting fixture 10. Placing theLEDs of the LED array 20 in thermal contact along the upper side of theheatsink 18 allows any heat generated by the LEDs to be effectivelytransferred to the elongated fins on the bottom side of the heatsink 18for dissipation within the room in which the lighting fixture 10 ismounted. Again, the particular configuration of the lighting fixture 10illustrated in FIGS. 1-3 is merely one of the virtually limitlessconfigurations for lighting fixtures 10 in which the concepts of thepresent disclosure are applicable.

With continued reference to FIGS. 2 and 3, an electronics housing 26 isshown mounted at one end of the lighting fixture 10, and is used tohouse all or a portion of the electronics used to power and control theLED array 20. These electronics are coupled to the LED array 20 throughappropriate cabling 28. With reference to FIG. 4, the electronicsprovided in the electronics housing 26 may be divided into a drivermodule 30 and a communications module 32.

At a high level, the driver module 30 is coupled to the LED array 20through the cabling 28 and directly drives the LEDs of the LED array 20based on control information provided by the communications module 32.In one embodiment, the driver module 30 provides the primaryintelligence for the lighting fixture 10 and is capable of driving theLEDs of the LED array 20 in a desired fashion. The driver module 30 maybe provided on a single, integrated module or divided into two or moresub-modules depending the desires of the designer.

When the driver module provides the primary intelligence for thelighting fixture 10, the communications module 32 acts as an intelligentcommunication interface that facilitates communications between thedriver module 30 and other lighting fixtures 10, a remote control system(not shown), or a portable handheld commissioning tool 36, which mayalso be configured to communicate with a remote control system in awired or wireless fashion.

Alternatively, the driver module 30 may be primarily configured to drivethe LEDs of the LED array 20 based on instructions from thecommunications module 32. In such an embodiment, the primaryintelligence of the lighting fixture 10 is provided in thecommunications module 32, which effectively becomes an overall controlmodule with wired or wireless communication capability, for the lightingfixture 10. The lighting fixture 10 may share sensor data, instructions,and any other data with other lighting fixtures 10 in the lightingnetwork or with remote entities. In essence, the communications module32 facilitates the sharing of intelligence and data among the lightingfixtures 10 and other entities.

In the embodiment of FIG. 4, the communications module 32 may beimplemented on a separate printed circuit board (PCB) than the drivermodule 30. The respective PCBs of the driver module 30 and thecommunications module 32 may be configured to allow the connector of thecommunications module 32 to plug into the connector of the driver module30, wherein the communications module 32 is mechanically mounted, oraffixed, to the driver module 30 once the connector of thecommunications module 32 is plugged into the mating connector of thedriver module 30.

In other embodiments, a cable may be used to connect the respectiveconnectors of the driver module 30 and the communications module 32,other attachment mechanisms may be used to physically couple thecommunications module 32 to the driver module 30, or the driver module30 and the communications module 32 may be separately affixed to theinside of the electronics housing 26. In such embodiments, the interiorof the electronics housing 26 is sized appropriately to accommodate boththe driver module 30 and the communications module 32. In manyinstances, the electronics housing 26 provides a plenum rated enclosurefor both the driver module 30 and the communications module 32.

With the embodiment of FIG. 4, adding or replacing the communicationsmodule 32 requires gaining access to the interior of the electronicshousing 26. If this is undesirable, the driver module 30 may be providedalone in the electronics housing 26. The communications module 32 may bemounted outside of the electronics housing 26 in an exposed fashion orwithin a supplemental housing 34, which may be directly or indirectlycoupled to the outside of the electronics housing 26, as shown in FIG.5. The supplemental housing 34 may be bolted to the electronics housing26. The supplemental housing 34 may alternatively be connected to theelectronics housing using snap-fit or hook-and-snap mechanisms. Thesupplemental housing 34, alone or when coupled to the exterior surfaceof the electronics housing 26, may provide a plenum rated enclosure.

In embodiments where the electronics housing 26 and the supplementalhousing 34 will be mounted within a plenum rated enclosure, thesupplemental housing 34 may not need to be plenum rated. Further, thecommunications module 32 may be directly mounted to the exterior of theelectronics housing 26 without any need for a supplemental housing 34,depending on the nature of the electronics provided in thecommunications module 32, how and where the lighting fixture 10 will bemounted, and the like.

The latter embodiment wherein the communications module 32 is mountedoutside of the electronics housing 26 may prove beneficial when thecommunications module 32 facilitates wireless communications with theother lighting fixtures 10, the remote control system, or other networkor auxiliary device. In essence, the driver module 30 may be provided inthe plenum rated electronics housing 26, which may not be conducive towireless communications. The communications module 32 may be mountedoutside of the electronics housing 26 by itself or within thesupplemental housing 34 that is more conducive to wirelesscommunications. A cable may be provided between the driver module 30 andthe communications module 32 according to a defined communicationinterface. As an alternative, which is described in detail furtherbelow, the driver module 30 may be equipped with a first connector thatis accessible through the wall of the electronics housing 26. Thecommunications module 32 may have a second connector, which mates withthe first connector to facilitate communications between the drivermodule 30 and the communications module 32.

The embodiments that employ mounting the communications module 32outside of the electronics housing 26 may be somewhat less costeffective, but provide significant flexibility in allowing thecommunications module 32 or other auxiliary devices to be added to thelighting fixture 10, serviced, or replaced. The supplemental housing 34for the communications module 32 may be made of a plenum rated plasticor metal, and may be configured to readily mount to the electronicshousing 26 through snaps, screws, bolts, or the like, as well as receivethe communications module 32. The communications module 32 may bemounted to the inside of the supplemental housing 34 through snap-fits,screws, twistlocks, and the like. The cabling and connectors used forconnecting the communications module 32 to the driver module 30 may takeany available form, such as with standard category 5/6 (cat 5/6) cablehaving RJ45 connectors, edge card connectors, blind mate connectorpairs, terminal blocks and individual wires, and the like. Having anexternally mounted communications module 32 relative to the electronicshousing 26 that includes the driver module 30 allows for easy fieldinstallation of different types of communications modules 32 or moduleswith other functionality for a given driver module 30.

As illustrated in FIG. 5, the communications module 32 is mounted withinthe supplemental housing 34. The supplemental housing 34 is attached tothe electronics housing 26 with bolts. As such, the communicationsmodule 32 is readily attached and removed via the illustrated bolts.Thus, a screwdriver, ratchet, or wrench, depending on the type of headfor the bolts, is required to detach or remove the communications module32 via the supplemental housing 34.

As an alternative, the communications module 32 may be configured asillustrated in FIGS. 6A and 6B. In this configuration, thecommunications module 32 may be attached to the electronics housing 26of the lighting fixture 10 in a secure fashion and may subsequently bereleased from the electronics housing 26 without the need for boltsusing available snap-lock connectors, such as illustrated in U.S. patentapplication Ser. No. 13/868,021, which was previously incorporated byreference. Notably, the rear of the communication module housingincludes a male (or female) snap-lock connector (not shown), which isconfigured to securely and releasable engage a complementary female (ormale) snap-lock connector 38 on the electronics housing 26.

FIG. 6A illustrates the communications module 32 prior to being attachedto or just after being released from the electronics housing 26 of thelighting fixture 10. One surface of the electronics housing 26 of thelighting fixture 10 includes the snap-lock connector 38, which includesa female electrical connector that is flanked by openings that extendinto the electronics housing 26 of the lighting fixture 10. The openingscorrespond in size and location to the locking members (not shown) onthe back of the communications module 32. Further, the female electricalconnector leads to or is coupled to a PCB of the electronics for thedriver module 30. In this example, the male electrical connector of thecommunications module 32 is configured to engage the female electricalconnector, which is mounted in the electronics housing 26 of thelighting fixture 10.

As the communications module 32 is snapped into place on the electronicshousing 26 of the lighting fixture 10, as illustrated in FIG. 6B, themale electrical connector of the communications module 32 will engagethe female electrical connector of the driver module 30 as the fixturelocking members of the communications module 32 engage the respectiveopenings of the locking interfaces in the electronics housing 26. Atthis point, the communications module 32 is snapped into place to theelectronics housing 26 of the lighting fixture 10, and the respectivemale and female connectors of the communications module 32 and thedriver module 30 are fully engaged.

With reference to FIG. 7, the bottom of one embodiment of the lightingfixture 10 is illustrated in a perspective view. In this embodiment, asensor module 40 is shown integrated into exposed side of the heatsink18 at one end of the heatsink 18. The sensor module 40 may include oneor more sensors, such as occupancy sensors S_(O), ambient light sensorsS_(A), temperature sensors, sound sensors (microphones), image (still orvideo) sensors, and the like. If multiple sensors are provided, they maybe used to sense the same or different environmental conditions. Ifmultiple sensors are used to sense the same environmental conditions,different types of sensors may be used.

As illustrated, the sensor module includes an occupancy sensor 42 and anambient light sensor, which is internal to the occupancy sensor 42 andnot visible in FIG. 7. The ambient light sensor is associated with alight pipe 44, which is used to guide light to the internal ambientlight sensor. The sensor module 40 may slide into the end of theheatsink 18 and be held in place by an end cap 46. The end cap 46 may beattached to the heatsink 18 using two screws 48. For the purposes ofthis description, the term “screw” is defined broadly to cover anyexternally threaded fastener, including traditional screws that cannotthread with a nut or tapped fixtures and bolts that can thread with nutsor other tapped fixtures.

FIGS. 8A and 8B illustrate one embodiment of the sensor module 40, whichwas introduced in FIG. 7. Primary reference is made to the exploded viewof FIG. 8B. The sensor module 40 includes an upper housing 50 and alower housing 52, which are configured to attach to one another througha snap-fit connector or other attachment mechanism, such as screws. Aprinted circuit board (PCB) 54 mounts inside of the sensor module 40,and the various sensors will mount to, or at least connect to, the PCB54. In the illustrated embodiment, an ambient light sensor 56 and anoccupancy sensor 42 are mounted to the printed circuit board. Theambient light sensor 56 is positioned such that it is aligned directlybeneath the light pipe 44 when the light pipe 44 is inserted into alight pipe receptacle 64. The occupancy sensor 42 is aligned with anoccupancy sensor opening 58 in the upper housing 50. Typically, thebulbous end of the occupancy sensor 42 extends into and partiallythrough the occupancy sensor opening 58 when the sensor module 40 isassembled, as illustrated in FIG. 8A. In this example, the occupancysensor 42 is an off-the-shelf passive infrared (PIR) occupancy sensor.The PCB 54 includes a connector, cabling, or wiring harness (not shown)that connects it directly or indirectly to the driver module 30 or thecommunications module 32.

The sensor module 40 may also include opposing mountings tabs 60, whichare used to help attach the sensor module 40 to the heatsink 18. In thisembodiment, the outer edges of the mounting tabs 60 expand to formbulbous edges 62.

Turning now to FIG. 9, an electrical block diagram of a lighting fixture10 is provided according to one embodiment. Assume for purposes ofdiscussion that the driver module 30, communications module 32, and LEDarray 20 are ultimately connected to form the core electronics of thelighting fixture 10, and that the communications module 32 is configuredto bidirectionally communicate with other lighting fixtures 10, thecommissioning tool 36, or other control entity through wired or wirelesstechniques. In this embodiment, a standard communication interface and afirst, or standard, protocol are used between the driver module 30 andthe communications module 32. This standard protocol allows differentdriver modules 30 to communicate with and be controlled by differentcommunications modules 32, assuming that both the driver module 30 andthe communications module 32 are operating according to the standardprotocol used by the standard communication interface. The term“standard protocol” is defined to mean any type of known or futuredeveloped, proprietary, or industry-standardized protocol.

In the illustrated embodiment, the driver module 30 and thecommunications module 32 are coupled via communication and power buses,which may be separate or integrated with one another. The communicationbus allows the communications module 32 to receive information from thedriver module 30 as well as control the driver module 30. An exemplarycommunication bus is the well-known inter-integrated circuitry (I²C)bus, which is a serial bus and is typically implemented with a two-wireinterface employing data and clock lines. Other available buses include:serial peripheral interface (SPI) bus, Dallas SemiconductorCorporation's 1-Wire serial bus, universal serial bus (USB), RS-232,Microchip Technology Incorporated's UNI/O®, and the like.

In this embodiment, the driver module 30 is configured to collect datafrom the ambient light sensor S_(A) and the occupancy sensor S_(O) anddrive the LEDs of the LED array 20. The data collected from the ambientlight sensor S_(A) and the occupancy sensor S_(O) as well as any otheroperational parameters of the driver module 30 may be shared with thecommunications module 32. As such, the communications module 32 maycollect data about the configuration or operation of the driver module30 and any information made available to the driver module 30 by the LEDarray 20, the ambient light sensor S_(A), and the occupancy sensorS_(O). The collected data may be used by the communications module 32 tocontrol how the driver module 30 operates, may be shared with otherlighting fixtures 10 or control entities, or may be processed togenerate instructions that are sent to other lighting fixtures 10.Notably, the sensor module 40 may be coupled to the communications businstead of directly to the driver module 30, such that sensorinformation from the sensor module 40 may be provided to the drivermodule 30 or the communications module 32 via the communications bus.

The communications module 32 may also be controlled in whole or in partby a remote control entity, such as the commissioning tool 36 or anotherlighting fixture 10. In general, the communications module 32 willprocess sensor data and instructions provided by the other lightingfixtures 10 or remote control entities and then provide instructionsover the communication bus to the driver module 30. An alternative wayof looking at it is that the communications module 32 facilitates thesharing of the system's information, including occupancy sensing,ambient light sensing, dimmer switch settings, etc., and provides thisinformation to the driver module 30, which then uses its own internallogic to determine what action(s) to take. The driver module 30 willrespond by controlling the drive current or voltages provided to the LEDarray 20 as appropriate.

In certain embodiments, the driver module 30 includes sufficientelectronics to process an alternating current (AC) input signal (AC IN)and provide an appropriate rectified or direct current (DC) signalsufficient to power the communications module 32, and perhaps the LEDarray 20. As such, the communications module 32 does not requireseparate AC-to-DC conversion circuitry to power the electronics residingtherein, and can simply receive DC power from the driver module 30 overthe power bus. Similarly, the sensor module 40 may receive powerdirectly from the driver module 30 or via the power bus, which ispowered by the driver module 30 or other source. The sensor module 40may also be coupled to a power source (not shown) independently of thedriver and communications modules 30, 32.

In one embodiment, one aspect of the standard communication interface isthe definition of a standard power delivery system. For example, thepower bus may be set to a low voltage level, such as 5 volts, 12 volts,24 volts, or the like. The driver module 30 is configured to process theAC input signal to provide the defined low voltage level and providethat voltage over the power bus, thus the communications module 32 orauxiliary devices, such as the sensor module 40, may be designed inanticipation of the desired low voltage level being provided over thepower bus by the driver module 30 without concern for connecting to orprocessing an AC signal to a DC power signal for powering theelectronics of the communications module 32 or the sensor module 40.

With reference to FIG. 10, a block diagram of one embodiment of thecommunications module 32 is illustrated. The communications module 32includes control circuitry 66 and associated memory 68, which containsthe requisite software instructions and data to facilitate operation asdescribed herein. The control circuitry 66 may be associated with acommunication interface 70, which is to be coupled to the driver module30, directly or indirectly via the communication bus. The controlcircuitry 66 may be associated with a wired communication port 72, awireless communication port 74, or both, to facilitate wired or wirelesscommunications with other lighting fixtures 10, the commissioning tool36, and remote control entities. The wireless communication port 74 mayinclude the requisite transceiver electronics to facilitate wirelesscommunications with remote entities. The wired communication port 72 maysupport universal serial (USB), Ethernet, or like interfaces.

The capabilities of the communications module 32 may vary greatly fromone embodiment to another. For example, the communications module 32 mayact as a simple bridge between the driver module 30 and the otherlighting fixtures 10 or remote control entities. In such an embodiment,the control circuitry 66 will primarily pass data and instructionsreceived from the other lighting fixtures 10 or remote control entitiesto the driver module 30, and vice versa. The control circuitry 66 maytranslate the instructions as necessary based on the protocols beingused to facilitate communications between the driver module 30 and thecommunications module 32 as well as between the communications module 32and the remote control entities.

In other embodiments, the control circuitry 66 plays an important rolein coordinating intelligence and sharing data among the lightingfixtures 10 as well as providing significant, if not complete, controlof the driver module 30. While the communications module 32 may be ableto control the driver module 30 by itself, the control circuitry 66 mayalso be configured to receive data and instructions from the otherlighting fixtures 10 or remote control entities and use this informationto control the driver module 30. The communications module 32 may alsoprovide instructions to other lighting fixtures 10 and remote controlentities based on the sensor data from the associated driver module 30as well as the sensor data and instructions received from the otherlighting fixtures 10 and remote control entities.

Power for the control circuitry 66, memory 68, the communicationinterface 70, and the wired and/or wireless communication ports 72 and74 may be provided over the power bus via the power port. As notedabove, the power bus may receive its power from the driver module 30,which generates the DC power signal. As such, the communications module32 may not need to be connected to AC power or include rectifier andconversion circuitry. The power port and the communication port may beseparate or may be integrated with the standard communication interface.The power port and communication port are shown separately for clarity.In one embodiment, the communication bus is a 2-wire serial bus, whereinthe connector or cabling configuration may be configured such that thecommunication bus and the power bus are provided using four wires: data,clock, power, and ground. In alternative embodiments, an internal powersupply 76, which is associated with AC power or a battery is used tosupply power.

The communications module 32 may have a status indicator, such as an LED78 to indicate the operating state of the communication module. Further,a user interface 80 may be provided to allow a user to manually interactwith the communications module 32. The user interface 80 may include aninput mechanism, an output mechanism, or both. The input mechanism mayinclude one or more of buttons, keys, keypads, touchscreens, or thelike. The output mechanism may include one more LEDs, a display, or thelike. For the purposes of this application, a button is defined toinclude a push button switch, all or part of a toggle switch, rotarydial, slider, or any other mechanical input mechanism.

A description of an exemplary embodiment of the LED array 20, drivermodule 30, and the communications module 32 follows. As noted, the LEDarray 20 includes a plurality of LEDs, such as the LEDs 82 illustratedin FIGS. 11 and 12. With reference to FIG. 11, a single LED chip 84 ismounted on a reflective cup 86 using solder or a conductive epoxy, suchthat ohmic contacts for the cathode (or anode) of the LED chip 84 areelectrically coupled to the bottom of the reflective cup 86. Thereflective cup 86 is either coupled to or integrally formed with a firstlead 88 of the LED 82. One or more bond wires 90 connect ohmic contactsfor the anode (or cathode) of the LED chip 84 to a second lead 92.

The reflective cup 86 may be filled with an encapsulant material 94 thatencapsulates the LED chip 84. The encapsulant material 94 may be clearor contain a wavelength conversion material, such as a phosphor, whichis described in greater detail below. The entire assembly isencapsulated in a clear protective resin 96, which may be molded in theshape of a lens to control the light emitted from the LED chip 84.

An alternative package for an LED 82 is illustrated in FIG. 12 whereinthe LED chip 84 is mounted on a substrate 98. In particular, the ohmiccontacts for the anode (or cathode) of the LED chip 84 are directlymounted to first contact pads 100 on the surface of the substrate 98.The ohmic contacts for the cathode (or anode) of the LED chip 84 areconnected to second contact pads 102, which are also on the surface ofthe substrate 98, using bond wires 104. The LED chip 84 resides in acavity of a reflector structure 105, which is formed from a reflectivematerial and functions to reflect light emitted from the LED chip 84through the opening formed by the reflector structure 105. The cavityformed by the reflector structure 105 may be filled with an encapsulantmaterial 94 that encapsulates the LED chip 84. The encapsulant material94 may be clear or contain a wavelength conversion material, such as aphosphor.

In either of the embodiments of FIGS. 11 and 12, if the encapsulantmaterial 94 is clear, the light emitted by the LED chip 84 passesthrough the encapsulant material 94 and the protective resin 96 withoutany substantial shift in color. As such, the light emitted from the LEDchip 84 is effectively the light emitted from the LED 82. If theencapsulant material 94 contains a wavelength conversion material,substantially all or a portion of the light emitted by the LED chip 84in a first wavelength range may be absorbed by the wavelength conversionmaterial, which will responsively emit light in a second wavelengthrange. The concentration and type of wavelength conversion material willdictate how much of the light emitted by the LED chip 84 is absorbed bythe wavelength conversion material as well as the extent of thewavelength conversion. In embodiments where some of the light emitted bythe LED chip 84 passes through the wavelength conversion materialwithout being absorbed, the light passing through the wavelengthconversion material will mix with the light emitted by the wavelengthconversion material. Thus, when a wavelength conversion material isused, the light emitted from the LED 82 is shifted in color from theactual light emitted from the LED chip 84.

For example, the LED array 20 may include a group of BSY or BSG LEDs 82as well as a group of red LEDs 82. BSY LEDs 82 include an LED chip 84that emits bluish light, and the wavelength conversion material is ayellow phosphor that absorbs the blue light and emits yellowish light.Even if some of the bluish light passes through the phosphor, theresultant mix of light emitted from the overall BSY LED 82 is yellowishlight. The yellowish light emitted from a BSY LED 82 has a color pointthat falls above the Black Body Locus (BBL) on the 1976 CIE chromaticitydiagram wherein the BBL corresponds to the various color temperatures ofwhite light.

Similarly, BSG LEDs 82 include an LED chip 84 that emits bluish light;however, the wavelength conversion material is a greenish phosphor thatabsorbs the blue light and emits greenish light. Even if some of thebluish light passes through the phosphor, the resultant mix of lightemitted from the overall BSG LED 82 is greenish light. The greenishlight emitted from a BSG LED 82 has a color point that falls above theBBL on the 1976 CIE chromaticity diagram wherein the BBL corresponds tothe various color temperatures of white light.

The red LEDs 82 generally emit reddish light at a color point on theopposite side of the BBL as the yellowish or greenish light of the BSYor BSG LEDs 82. As such, the reddish light from the red LEDs 82 may mixwith the yellowish or greenish light emitted from the BSY or BSG LEDs 82to generate white light that has a desired color temperature and fallswithin a desired proximity of the BBL. In effect, the reddish light fromthe red LEDs 82 pulls the yellowish or greenish light from the BSY orBSG LEDs 82 to a desired color point on or near the BBL. Notably, thered LEDs 82 may have LED chips 84 that natively emit reddish lightwherein no wavelength conversion material is employed. Alternatively,the LED chips 84 may be associated with a wavelength conversionmaterial, wherein the resultant light emitted from the wavelengthconversion material and any light that is emitted from the LED chips 84without being absorbed by the wavelength conversion material mixes toform the desired reddish light.

The blue LED chip 84 used to form either the BSY or BSG LEDs 82 may beformed from a gallium nitride (GaN), indium gallium nitride (InGaN),silicon carbide (SiC), zinc selenide (ZnSe), or like material system.The red LED chip 84 may be formed from an aluminum indium galliumnitride (AlInGaP), gallium phosphide (GaP), aluminum gallium arsenide(AlGaAs), or like material system. Exemplary yellow phosphors includecerium-doped yttrium aluminum garnet (YAG:Ce), yellow BOSE (Ba, O, Sr,Si, Eu) phosphors, and the like. Exemplary green phosphors include greenBOSE phosphors, Lutetium aluminum garnet (LuAg), cerium doped LuAg(LuAg:Ce), Maui M535 from Lightscape Materials, Inc. of 201 WashingtonRoad, Princeton, N.J. 08540, and the like. The above LED architectures,phosphors, and material systems are merely exemplary and are notintended to provide an exhaustive listing of architectures, phosphors,and materials systems that are applicable to the concepts disclosedherein.

The International Commission on Illumination (Commission internationalede l≢éclairage, or CIE) has defined various chromaticity diagrams overthe years. The chromaticity diagrams are used to project a color spacethat represents all human perceivable colors without reference tobrightness or luminance. FIG. 13 illustrates a CIE 1976 chromaticitydiagram, which includes a portion of a Planckian locus, or black bodylocus (BBL). The BBL is a path within the color space that the color ofan incandescent black body would travel as the temperature of the blackbody changes. While the color of the incandescent body may range from anorangish-red to blue, the middle portions of the path encompass what istraditionally considered as “white light.”

Correlated Color Temperature (CCT), or color temperature, is used tocharacterize white light. CCT is measured in kelvin (K) and defined bythe Illuminating Engineering Society of North America (IESNA) as “theabsolute temperature of a blackbody whose chromaticity most nearlyresembles that of the light source.” Light output that is:

-   -   below 3200 K is a yellowish white and generally considered to be        warm (white) light;    -   between 3200 K and 4000 K is generally considered neutral        (white) light; and    -   above 4000 K is bluish-white and generally considered to be cool        (white) light.

The coordinates (u′, v′) are used to define color points within thecolor space of the CIE 1976 chromaticity diagram. The v′ value defines avertical position and the u′ value defines a horizontal position. As anexample, the color points for a first BSY LED 82 is about (0.1900,0.5250), a second BSY LED 82 is about (0.1700, 0.4600), and a red LED 82is about (0.4900, 0.5600). Notably, the first and second BSY LEDs 82 aresignificantly spaced apart from one another along the v′ axis. As such,the first BSY LED 82 is much higher than the second BSY LED 82 in thechromaticity diagram. For ease of reference, the higher, first BSY LED82 is referenced as the high BSY-H LED, and the lower, second BSY LED 82is referenced as the low BSY-L LED.

As such, the ΔV′ for the high BSY-H LED and the low BSY-L LED is about0.065 in the illustrated example. In different embodiments, the Δv′ maybe greater than 0.025, 0.030, 0.033, 0.040 0.050, 0.060, 0.075, 0.100,0.110, and 0.120, respectively. Exemplary, but not absolute upper boundsfor Δv′ may be 0.150, 0.175, or 0.200 for any of the aforementionedlower bounds. For groups of LEDs of a particular color, the Δv′ betweentwo groups of LEDs is the difference between the average v′ values foreach group of LEDs. As such, the Δv′ between groups of LEDs of aparticular color may also be greater than 0.030, 0.033, 0.040 0.050,0.060, 0.075, 0.100, 0.110, and 0.120, respectively, with the same upperbounds as described above. Further, the variation of color points amongthe LEDs 82 within a particular group of LEDs may be limited to within aseven, five, four, three, or two-step MacAdam ellipse in certainembodiments. In general, the greater the delta v′, the larger the rangethrough which the CCT of the white light can be adjusted along the blackbody locus. The closer the white light is to the black body locus, themore closely the white light will replicate that of an incandescentradiator.

In one embodiment, the LED array 20 includes a first LED group of onlylow BSY-L LEDs, a second LED group of only high BSY-H LEDs, and a thirdLED group of only red LEDs. The currents used to drive the first,second, and third LED groups may be independently controlled such thatthe intensity of the light output from the first, second, and third LEDgroups is independently controlled. As such, the light output for thefirst, second, and third LED groups may be blended or mixed to create alight output that has an overall color point virtually anywhere within atriangle formed by the color points of the respective low BSY-L LEDs,high BSY-H LEDs, and the red LEDs. Within this triangle resides asignificant portion of the BBL, and as such, the overall color point ofthe light output may be dynamically adjusted to fall along the portionof the BBL that resides within the triangle.

A crosshatch pattern highlights the portion of the BBL that falls withinthe triangle. Adjusting the overall color point of the light outputalong the BBL corresponds to adjusting the CCT of the light output,which as noted above is considered white light when falling on the BBL.In one embodiment, the CCT of the overall light output may be adjustedover a range from about 2700 K to about 5700 K. In another embodiment,the CCT of the overall light output may be adjusted over a range fromabout 3000 K to 5000 K. In yet another embodiment, the CCT of theoverall light output may be adjusted over a range from about 2700 K to5000 K. In yet another embodiment, the CCT of the overall light outputmay be adjusted over a range from about 3000 K to 4000 K. Thesevariations in CCT can be accomplished while maintaining a high colorrendering index value (CRI), such as a CRI equal to or greater than 90.

To be considered “white” light, the overall color point does not have tofall precisely on the BBL. Unless defined otherwise and for the purposesof this application only, a color point within a five-step MacAdamellipse of the BBL is defined as white light on the BBL. For tightertolerances, four, three, and two-step MacAdam ellipses may be defined.

As noted, the LED array 20 may include a mixture of red LEDs 82, highBSY-H LEDs 82, and low BSY-L LEDs 82. The driver module 30 for drivingthe LED array 20 is illustrated in FIG. 14, according to one embodimentof the disclosure. The LED array 20 may be divided into multiple stringsof series connected LEDs 82. In essence, LED string S1, which includes anumber of red LEDs (RED), forms a first group of LEDs 82. LED string S2,which includes a number of low BSY LEDs (BSY-L), forms a second group ofLEDs 82. And, LED string S3, which includes a number of high BSY LEDs(BSY-H), forms a third group of LEDs 82.

For clarity, the various LEDs 82 of the LED array 20 are referenced asRED, BSY-L, and BSY-H in FIG. 14 to clearly indicate which LEDs arelocated in the various LED strings S1, S2, and S3. While BSY LEDs 82 areillustrated, BSG or other phosphor-coated, wavelength converted LEDs maybe employed in analogous fashion. For example, a string of high BSG-HLEDs 82 may be combined with a string of low BSG-L LEDs 82, and viceversa. Further, a string of low BSY-H LEDs may be combined with a stringof high BSG-H LEDs, and vice versa. Non-phosphor-coated LEDs, such asnon-wavelength converted red, green, and blue LEDs, may also be employedin certain embodiments.

In general, the driver module 30 controls the currents i₁, i₂, and i₃,which are used to drive the respective LED strings S1, S2, and S3. Theratio of currents i₁, i₂, and i₃ that are provided through respectiveLED strings S1, S2, and S3 may be adjusted to effectively control therelative intensities of the reddish light emitted from the red LEDs 82of LED string S1, the yellowish/greenish light emitted from the lowBSY-L LEDs 82 of LED string S2, and the yellow/greenish light emittedfrom the high BSY-H LEDs 82 of LED string S3. The resultant light fromeach LED string S1, S2, and S3 mixes to generate an overall light outputthat has a desired color, CCT, and intensity, the later of which mayalso be referred to a dimming level. As noted, the overall light outputmay be white light that falls on or within a desired proximity of theBBL and has a desired CCT.

The number of LED strings Sx may vary from one to many and differentcombinations of LED colors may be used in the different strings. EachLED string Sx may have LEDs 82 of the same color, variations of the samecolor, or substantially different colors. In the illustrated embodiment,each LED string S1, S2, and S3 is configured such that all of the LEDs82 that are in the string are all essentially identical in color.However, the LEDs 82 in each string may vary substantially in color orbe completely different colors in certain embodiments. In anotherembodiment, three LED strings Sx with red, green, and blue LEDs may beused, wherein each LED string Sx is dedicated to a single color. In yetanother embodiment, at least two LED strings Sx may be used, whereindifferent colored BSY or BSG LEDs are used in one of the LED strings Sxand red LEDs are used in the other of the LED strings Sx. A singlestring embodiment is also envisioned, where currents may be individuallyadjusted for the LEDs of the different colors using bypass circuits, orthe like.

The driver module 30 depicted in FIG. 14 generally includes AC-DCconversion circuitry 106, control circuitry 110, and a number of currentsources, such as the illustrated DC-DC converters 112. The AC-DCconversion circuitry 106 is adapted to receive an AC power signal (ACIN), rectify the AC power signal, correct the power factor of the ACpower signal, and provide a DC output signal. The DC output signal maybe used to directly power the control circuitry 110 and any othercircuitry provided in the driver module 30, including the DC-DCconverters 112, a communication interface 114, as well as the sensormodule 40.

The DC output signal may also be provided to the power bus, which iscoupled to one or more power ports, which may be part of the standardcommunication interface. The DC output signal provided to the power busmay be used to provide power to one or more external devices that arecoupled to the power bus and separate from the driver module 30. Theseexternal devices may include the communications module 32 and any numberof auxiliary devices, such as the sensor module 40. Accordingly, theseexternal devices may rely on the driver module 30 for power and can beefficiently and cost effectively designed accordingly. The AC-DCconversion circuitry 108 of the driver module 30 is robustly designed inanticipation of being required to supply power to not only its internalcircuitry and the LED array 20, but also to supply power to theseexternal devices. Such a design greatly simplifies the power supplydesign, if not eliminating the need for a power supply, and reduces thecost for these external devices.

As illustrated, the three respective DC-DC converters 112 of the drivermodule 30 provide currents i₁, i₂, and i₃ for the three LED strings S1,S2, and S3 in response to control signals CS1, CS2, and CS3. The controlsignals CS1, CS2, and CS3 may be pulse width modulated (PWM) signalsthat effectively turn the respective DC-DC converters on during a logichigh state and off during a logic low state of each period of the PWMsignal. In one embodiment the control signals CS1, CS2, and CS3 are theproduct of two PWM signals.

The first PWM signal is a higher frequency PWM signal that has a dutycycle that effectively sets the DC current level through a correspondingone of LED strings S1, S2, and S3, when current is allowed to passthrough the LED strings S1, S2, and S3. The second PWM signal is a lowerfrequency signal that has a duty cycle that corresponds a desireddimming or overall output level. In essence, the higher frequency PWMsignals set the relative current levels though each LED string S1, S2,and S3 while the lower frequency PWM signal determines how long thecurrents i₁, i₂, and i₃ are allowed to pass through the LED strings S1,S2, and S3 during each period of the lower frequency PWM signal. Thelonger the currents i₁, i₂, and i₃ are allowed to flow through the LEDstrings S1, S2, and S3 during each period, the higher the output level,and vice versa. Given the reactive components associated with the DC-DCconverters 112, the relative current levels set with the higherfrequency PWM signals may be filtered to a relative DC current. However,this DC current is essentially pulsed on and off based on the duty cycleof the lower frequency PWM signal. For example, the higher frequency PWMsignal may have a switching frequency of around 200 KHz, while the lowerfrequency PWM signal may have a switching frequency of around 1 KHz.

In certain instances, a dimming device may control the AC power signal.The AC-DC conversion circuitry 106 may be configured to detect therelative amount of dimming associated with the AC power signal andprovide a corresponding dimming signal to the control circuitry 110.Based on the dimming signal, the control circuitry 110 will adjust thecurrents i₁, i₂, and i₃ provided to each of the LED strings S1, S2, andS3 to effectively reduce the intensity of the resultant light emittedfrom the LED strings S1, S2, and S3 while maintaining the desired CCT.As described further below, the CCT and dimming levels may be initiatedinternally or received from the commissioning tool 36, a wallcontroller, or another lighting fixture 10. If received from an externaldevice via the communications module 32, the CCT and/or dimming levelsare delivered from the communications module 32 to the control circuitry110 of the driver module 30 in the form of a command via thecommunication bus. The driver module 30 will respond by controlling thecurrents i₁, i₂, and i₃ in the desired manner to achieve the requestedCCT and/or dimming levels.

The intensity and CCT of the light emitted from the LEDs 82 may beaffected by temperature. If associated with a thermistor S_(T) or othertemperature-sensing device, the control circuitry 110 can control thecurrents i₁, i₂, and i₃ provided to each of the LED strings S1, S2, andS3 based on ambient temperature of the LED array 20 in an effort tocompensate for temperature effects. The control circuitry 110 may alsomonitor the output of the occupancy and ambient light sensors S_(O) andS_(A) for occupancy and ambient light information and further controlthe currents i₁, i₂, and i₃ in a desired fashion. Each of the LEDstrings S1, S2, and S3 may have different temperature compensationadjustments, which may also be functions of the magnitude of the variouscurrents i₁, i₂, and i₃.

The control circuitry 110 may include a central processing unit (CPU)and sufficient memory 116 to enable the control circuitry 110 tobidirectionally communicate with the communications module 32 or otherdevices over the communication bus through an appropriate communicationinterface (I/F) 114 using a defined protocol, such as the standardprotocol described above. The control circuitry 110 may receiveinstructions from the communications module 32 or other device and takeappropriate action to implement the received instructions. Theinstructions may range from controlling how the LEDs 82 of the LED array20 are driven to returning operational data, such as temperature,occupancy, light output, or ambient light information, that wascollected by the control circuitry 110 to the communications module 32or other device via the communication bus. Notably, the functionality ofthe communications module 32 may be integrated into the driver module30, and vice versa.

With reference to FIG. 15, an exemplary way to control the currents i₁,i₂, and i₃, which are provided to the respective LED strings S1, S2, andS3 is illustrated, such that the CCT of the overall light output can befinely tuned over a relatively long range and throughout virtually anydimming level. As noted above, the control circuitry 110 generatescontrol signals CS1, CS2, and CS3, which control the currents i₁, i₂,and i₃. Those skilled in the art will recognize other ways to controlthe currents i₁, i₂, and i₃.

In essence, the control circuitry 110 of the driver module 30 is loadedwith a current model in the form of one or more functions (equation) orlook up tables for each of the currents i₁, i₂, and i₃. Each currentmodel is a reference model that is a function of dimming or outputlevel, temperature, and CCT. The output of each model provides acorresponding control signal CS1, CS2, and CS3, which effectively setsthe currents i₁, i₂, and i₃ in the LED strings S1, S2, and S3. The threecurrent models are related to each other. At any given output level,temperature, and CCT, the resulting currents i₁, i₂, and i₃ cause theLED strings S1, S2, and S3 to emit light, which when combined, providesan overall light output that has a desired output level and CCT,regardless of temperature. While the three current models do not need tobe a function of each other, they are created to coordinate with oneanother to ensure that the light from each of the strings S1, S2, and S3mix with one another in a desired fashion.

With reference to FIG. 16, an exemplary process for generating thecontrol signals CS1, CS2, and CS3 is provided. Initially, assume thatthe current models are loaded in the memory 116 of the control circuitry110. Further assume that the current models are reference models for theparticular type of lighting fixture 10.

Further assume that the desired CCT is input to a color change function118, which is based on the reference models. The color change function118 selects reference control signals R1, R2, and R3 for each of thecurrents i₁, i₂, and i₃ based on the desired CCT. Next, the referencecontrol signals R1, R2, and R3 are each adjusted, if necessary, by acurrent tune function 120 based on a set of tuning offsets. The turningoffsets may be determined through a calibration process duringmanufacturing or testing and uploaded into the control circuitry 110.The tuning offset correlates to a calibration adjustment to the currentsi₁, i₂, and i₃ that should be applied to get the CCT of the overalllight output to match a reference CCT. Details about the tuning offsetsare discussed further below. In essence, the current tune function 120modifies the reference control signals R1, R2, and R3 based on thetuning offsets to provide tuned control signals T1, T2, and T3.

In a similar fashion, the temperature compensation function 122 modifiesthe tuned control signals T1, T2, and T3 based on the currenttemperature measurements to provide temperature compensated controlsignals TC1, TC2, and TC3. Since light output from the various LEDs 82may vary in intensity and color over temperature, the temperaturecompensation function 122 effectively adjusts the currents i₁, i₂, andi₃ to substantially counter the effect of these variations. Thetemperature sensor S_(T) may provide the temperature input and isgenerally located near the LED array 20.

Finally, the dimming function 124 modifies the temperature compensatedcontrol signals TC1, TC2, and TC3 based on the desired dimming (output)levels to provide the controls signals CS1, CS2, and CS3, which drivethe DC-DC converters 112 to provide the appropriate currents i₁, i₂, andi₃ to the LED strings S1, S2, and S3. Since light output from thevarious LEDs 82 may also vary in relative intensity and color overvarying current levels, the dimming function 124 helps to ensure thatthe CCT of the overall light output corresponds to the desired CCT andintensity at the selected dimming (output) levels.

A wall controller, commissioning tool 36, or other lighting fixture 10may provide the CCT setting and dimming levels. Further, the controlcircuitry 110 may be programmed to set the CCT and dimming levelsaccording to a defined schedule, state of the occupancy and ambientlight sensors S_(O) and S_(A), other outside control input, time of day,day of week, date, or any combination thereof. For example, these levelsmay be controlled based on a desired efficiency or correlated colortemperature.

These levels may be controlled based the intensity (level) and/orspectral content of the ambient light, which is measured by the ambientlight sensor S_(A). When controlled based on spectral content, thedimming or CCT levels may be adjusted based on the overall intensity ofthe ambient light. Alternatively, the dimming levels, color point, orCCT levels may be adjusted to either match the spectral content of theambient light or help fill in spectral areas of the ambient light thatare missing or attenuated. For example, if the ambient light isdeficient in a cooler area of the spectrum, the light output may beadjusted to provide more light in that cooler area of the spectrum, suchthat the ambient light and light provided by the lighting fixtures 10combine to provide a desired spectrum. CCT, dimming, or color levels mayalso be controlled based on power conditions (power outage, batterybackup operation, etc.), or emergency conditions (fire alarm, securityalarm, weather warning, etc.).

As noted, the tuning offset is generally determined during manufacture,but may also be determined and loaded into the lighting fixture 10 inthe field. The tuning offset is stored in memory 116 and correlates to acalibration adjustment to the currents i₁, i₂, and i₃ that should beapplied to get the CCT of the overall light output to match a referenceCCT. With reference to FIG. 17, exemplary current curves are providedfor reference (pre-tuned) currents and tuned (post-tuned) currents i₁,i₂, and i₃ over a CCT range of about 3000 K to 5000 K. The referencecurrents represent the currents i₁, i₂, and i₃ that are expected toprovide a desired CCT in response to the reference control signals R1,R2, and R3 for the desired CCT. However, the actual CCT that is providedin response to the reference currents i₁, i₂, and i₃ may not match thedesired CCT based on variations in the electronics in the driver module30 and the LED array 20. As such, the reference currents i₁, i₂, and i₃may need to be calibrated or adjusted to ensure that the actual CCTcorresponds to the desired CCT. The tuning offset represents thedifference between the curves for the model and tuned currents i₁, i₂,and i₃.

For single-point calibration, the tuning offset may be fixed multipliersthat can be applied over the desired CCT range for the correspondingreference currents i₁, i₂, and i₃. Applying the fixed multipliersrepresents multiplying the reference currents i₁, i₂, and i₃ bycorresponding percentages. In FIG. 13, the tuning offsets for thereference currents i₁, i₂, and i₃ may be 0.96 (96%), 1.04 (104%), and1.06 (106%), respectively. As such, as reference currents i₂, and i₃increase, the tuned currents i₂, and i₃ will increase at a greater rate.As reference current i₁ increases, the tuned current i₁ will increase ata lessor rate.

For example, a single calibration may take place at 25 C and a CCT of4000 K wherein the tuning offsets are determined for each of thecurrents i₁, i₂, and i₃. The resultant tuning offsets for the currentsi₁, i₂, and i₃ at 25 C and 4000 K may be applied to the respective modelcurrent curves. The effect is to shift each current curve up or down bya fixed percentage. As such, the same tuning offsets that are needed forcurrents i₁, i₂, and i₃ at 4000 K are applied at any selected CCTbetween 3000 K and 5000 K. The tuning offsets are implemented bymultiplying the reference control signals R1, R2, and R3 by a percentagethat causes the currents i₁, i₂, and i₃ to increase or decrease. Asnoted above, the reference control signals R1, R2, and R3 are alteredwith the tuning offsets to provide the tuned control signals T1, T2, andT3. The tuned control signals T1, T2, and T3 may be dynamically adjustedto compensate for temperature and dimming (output) levels.

While the fixed percentage-based tuning offsets may be used forcalibration and manufacturing efficiency, other tuning offsets may bederived and applied. For example, the tuning offsets may be fixedmagnitude offsets that are equally applied to all currents regardless ofthe CCT value. In a more complex scenario, an offset function can bederived for each of the currents i₁, i₂, and i₃ and applied to thecontrol signals CS1, CS2, and CS3 over the CCT range.

The lighting fixture 10 need not immediately change from one CCT levelto another in response to a user or other device changing the selectedCCT level. The lighting fixture 10 may employ a fade rate, whichdictates the rate of change for CCT when transitioning from one CCTlevel to another. The fade rate may be set during manufacture, by thecommissioning tool 36, wall controller, or the like. For example, thefade rate could be 500 K per second. Assume the CCT levels for a 5%dimming level and a 100% dimming level are 3000 K and 5000 K,respectively. If the user or some event changed the dimming level from5% to 100%, the CCT level may transition from 3000 K to 5000 K at a rateof 500 K per second. The transition in this example would take twoseconds. The dimming rate may or may not coincide with the CCT faderate. With a fade rate, changes in the selected CCT level may betransitioned in a gradual fashion to avoid abrupt switches from one CCTlevel to another.

With reference to FIG. 18, an exemplary wall controller 126 isillustrated. The wall controller 126 is shown in this embodiment withthree buttons: an on-off button 130, a dimming button 132, and a CCTbutton 134. As will be described further below, the wall controller 126may be hardwired to one or more lighting fixtures 10 or be configured towirelessly communicate directly or indirectly with one or more lightingfixtures 10. The wired or wireless communications will support deliveryof signals, messages, or instructions, which are hereafter referred toas signals, to the lighting fixtures 10. The wall controllers 126 may beconfigured to simply relay the various user inputs to the associatedlighting fixture(s) 10 as soon as the user inputs are received. In thiscase, the lighting fixtures 10 will process the user inputs to determinethe appropriate response to take. When the wall controllers 126 actprimarily as a relay, the primary intelligence, or decision-makingcapability, resides in the lighting fixture(s) 10. Alternatively,significant processing and decision-making capability may be provided inthe wall controller 126, wherein the wall controller 126 may process thevarious user inputs and determine how to instruct the lightingfixture(s) 10 based on various criteria, such as program rules, sensorinformation from local or remote sensors, prior user input, and thelike.

When discussing the various examples described below, either of theseconfigurations, or combination thereof, may be employed. For the relayembodiment, the user input is relayed to one or more lighting fixtures10, which will process the user input and provide the requisite lightingresponse. When the wall controller 126 needs to provide a userperceptible response, the response may be initiated internally by thewall controller 126 based on available information or provided inresponse to instructions received from the lighting fixture 10. Forexample, if the wall controller 126 needs to control an LED that islocated on the wall controller 126 to provide user feedback, this may beinitiated internally or in response to a signal from a lighting fixture10. With a more intelligent wall controller 126, the wall controller 126may simply instruct the associated lighting fixture 10 to provide aspecific lighting response, such as dim to 50% with a CCT of 3500 K, andcontrol the LED accordingly. The lighting fixture 10 need not be awareof the LED control in this case.

When equipped for wireless communications, the wall controller 126 mayact as a node in a multi-node wireless mesh network wherein certainnodes are lighting fixtures 10. For further information regardingmesh-network based lighting networks, reference is made to U.S. patentapplication Ser. No. 13/782,022, filed Mar. 1, 2013; U.S. patentapplication Ser. No. 13/782,040, filed Mar. 1, 2013; U.S. patentapplication Ser. No. 13/782,053, filed Mar. 1, 2013; U.S. patentapplication Ser. No. 13/782,068, filed Mar. 1, 2013; U.S. patentapplication Ser. No. 13/782,078, filed Mar. 1, 2013; U.S. patentapplication Ser. No. 13/782,096, filed Mar. 1, 2013; U.S. patentapplication Ser. No. 13/782,131, filed Mar. 1, 2013; U.S. patentapplication Ser. No. 13/838,398, filed Mar. 15, 2013; U.S. patentapplication Ser. No. 13/868,021, filed Apr. 22, 2013; and U.S.provisional patent application No. 61/932,058, filed Jan. 27, 2014,which are incorporated herein by reference in their entireties.

With the embodiment illustrated in FIG. 18, each of the three buttons(130, 132, 134) are shown as rocker switches wherein pressing the tophalf of the button invokes a first lighting control response and thepressing the bottom half of the button invokes a second lighting controlresponse. For the on-off button 130, pressing the top half will resultin the wall controller 126 sending a signal to turn on any associatedlighting fixture(s) 10. Pressing the bottom half of the on-off button130 will result in the wall controller sending a signal to turn off theassociated lighting fixture(s) 10. As with any of these signals, thesignals may be sent directly or indirectly through a network to theassociated lighting fixture(s) 10.

The dimming button 132 is used to vary the light output level, ordimming level, of the associated lighting fixture(s) 10. For the dimmingbutton 132, pressing the top half will result in the wall controller 126sending a signal to increase the output light level of the associatedlighting fixture(s) 10. Pressing the bottom half of the dimming button132 will result in the wall controller sending a signal to decrease theoutput light level of the associated lighting fixture(s) 10. With eachpress of the top half or bottom half of the dimming button 132, theassociated lighting fixture(s) 10 may be instructed to increase ordecrease their output light levels by a defined amount. If the top halfor bottom half of the dimming button 132 is held down, the associatedlighting fixture(s) 10 may be instructed to continuously increase ordecrease their output levels until the dimming button 132 is released.

The CCT button 134 is used to vary the CCT of the light output of theassociated lighting fixture(s) 10. For the CCT button 134, pressing thetop half will result in the wall controller 126 sending a signal toincrease the CCT level of the associated lighting fixture(s) 10.Pressing the bottom half of the CCT button 134 will result in the wallcontroller sending a signal to decrease the CCT level of the associatedlighting fixture(s) 10. With each press of the top half or bottom halfof the CCT button 134, the associated lighting fixture(s) 10 may beinstructed to increase or decrease their CCT by a defined amount. Forexample, each press of the top half or bottom half of the dimming button132 may result in an increase or decrease of the CCT of the light outputof the associated lighting fixture(s) 10 by 100 K. Alternately, eachpress could result in a 1, 5, 10, 50, 100, 250, or 500 K change in lightoutput. If the top half or bottom half of the dimming button 132 is helddown, the associated lighting fixture(s) 10 may be instructed tocontinuously increase or decrease their CCT levels until the CCT button134 is released. The rate of change may be fixed or may change based onhow long the CCT button 134 is held down. The longer the CCT button 134is depressed, the faster the change in CCT.

A variation of the wall controller 126 of FIG. 18 is shown in FIG. 19.In this embodiment, a first CCT LED 136 is provided directly above theCCT button 134; however, the first CCT LED 136 could be providedanywhere on the wall controller 126. As with any of the featuresdescribed in the embodiments, the first CCT LED 136 may be included withany feature and part of any embodiment of the invention. The first CCTLED 136 may be a variable color LED, which can output light of differentcolors and intensities depending on how it is driven. For example, thefirst CCT LED 136 may be configured to output light ranging from red towhite to blue through a color spectrum in a continuous or graduatedfashion. The particular color or brightness of the light provided by thefirst CCT LED 136 may correspond to the particular CCT level being setby the wall controller 126 in response to a user adjusting the CCT usingthe CCT button 134. For example, assume that the wall controller 126 isable to vary the CCT of any associated lighting fixtures 10 from 3000 Kto 5000 K in 100 K increments. When the user has used the CCT button 134to select the lowest CCT (3000 K), which corresponds to a warmer CCT,the first CCT LED 136 will be driven to omit a red light. When the userhas used the CCT button 134 to select the highest CCT (5000 K), whichcorresponds to a cooler CCT, the first CCT LED 136 will be driven toomit a blue light. When the user has used the CCT button 134 to selectthe mid-ranged CCT (4000 K), which corresponds to a relatively neutralCCT, the first CCT LED 136 will be driven to omit a white light.

For those relatively warmer CCT levels between 3000 K and 4000 K, thelight emitted from the first CCT LED 136 may transition gradually fromred to orange to yellow to white, as the CCT level progresses in 100 Kincrements from 3000 K to 4000 K. For those relatively cooler CCTslevels between 4000 K and 5000 K, the light emitted from the first CCTLED 136 may transition gradually from white to green to blue, as the CCTlevel progresses in 100 K increments from 4000 K to 5000 K. In analternative to gradually changing colors along the visible lightspectrum to indicate relative CCT level, the first CCT LED 136 could bedriven to change in intensity, wherein the warmer the CCT Level, thebrighter the red light emitted will be. Conversely, the cooler the CCTlevel, the brighter the blue light emitted will be. The LED may be offor a very dim red, white, or blue at the mid-range CCT level. Thoseskilled in the art will recognize various ways to drive the first CCTLED 136 in a manner that causes the light emitted from the first CCT LED136 to correspond in output, whether it is color, dimming level, or acombination thereof, to the current CCT level of the lighting fixture(s)10 being controlled by the wall controller 126.

The wall controller 126 may control the first CCT LED 136 to emit lightthat is indicative of the CCT level continuously, when a user ischanging the CCT level using the CCT button 134 and perhaps for a shortwhile thereafter, or on a periodic basis. In the latter case, the firstCCT LED 136 may flash periodically to provide an indication of CCTlevel.

FIG. 20 illustrates an alternative configuration for the wall controller126. In essence, the operation and functionality of this wall controller126 is analogous to that described above in association with FIG. 19.Instead of having a separate dimming button 132 and CCT button 134, amultifunction button 138 is provided along with a selection switch 140.The selection switch 140 can be toggled between a dim mode and a CCTmode. When in the dim mode, the multifunction button 138 operates likethe dimming button 132. When in the CCT mode, the multifunction button138 operates like the CCT button 134. Optionally, the first CCT LED 136may be provided as described above and used such that the user hasfeedback as to the current or selected CCT level.

Another embodiment of the wall controller 126 is illustrated in FIG. 21.The wall controller 126 has an on-off button 130 and a dimming button132 that operates as described above. The wall controller 126 alsoincludes a first CCT LED 136 and a second CCT LED 142. As illustrated,the first CCT LED 136 is located above the dimming button 132, and thesecond CCT LED 142 is located below the dimming button 132. The firstCCT LED 136 is part of or associated with a first CCT button 144, andthe second CCT LED 142 is part of or associated with a second CCT button146. In the illustrated embodiment, the first CCT LED 136 and first CCTbutton 144 form a first push button switch, and the second CCT LED 142and the second CCT button 146 form a second push button switch.

In one embodiment, the wall controller 126 may have minimum and maximumdimming levels that are selectable through interaction with the dimmingbutton 132. The maximum dimming level may set to 100% of the maximumlight output level or less (i.e. 90% of the maximum light output level).The minimum setting may be completely off or at lower dimming level,such as 5% of the maximum light output level. For the purposes ofillustration only, assume that the maximum dimming level corresponds to100% of the maximum light output level and that the minimum dimminglevel corresponds to 5% of the maximum light output level.

The wall controller 126 allows a user to select a first CCT level forthe maximum dimming level using the first CCT button 144 and a secondCCT level for the minimum dimming level using the second CCT button 146.The respective first and second CCT LEDs 136, 142 are used to providefeedback for the current or selected maximum and minimum CCT levels,respectively. For example, the first and second CCT LEDs 136, 142 may becontrolled to cycle through a series of colors that sweep from red toblue though white to indicate the relative CCT levels (i.e. 3000 K(red), 4000 K (white), and 5000 K (blue)).

The wall controller 126 will thus receive user input via the first andsecond CCT buttons 144, 146 to set the first and second CCT levels forthe corresponding maximum and minimum dimming levels. Once the first andsecond CCT levels are identified, the CCT level of the lighting fixtures10 will transition from the second CCT level to the first CCT level asthe dimming level changes from the minimum dimming level to the maximumdimming level.

For example, the wall controller 126 may receive user input via thefirst and second CCT buttons 144, 146 to set the first and second CCTlevels to 5000 K and 3000 K, respectively. Assume the correspondingmaximum and minimum dimming levels, which are 100% and 5%, respectively.Once the CCT levels are set, the wall controller 126 will sendinstructions to the lighting fixtures 10 to transition the CCT levelfrom 3000 K to 5000 K as the dimming level changes from the minimumdimming level (5%) to the maximum dimming level (100%). The CCT levelsand dimming levels will vary from application to application. Further,the lower dimming levels need not be associated with lower CCT levels,as the inverse may be desired in certain applications.

FIG. 22 illustrates another variation on the concepts of FIG. 21. Inthis embodiment, the first and second CCT LEDs 136 and 142 are eachformed by an array of LEDs. The LEDs in each array may be differentcolored LEDs or may be controlled to emit different colors of light,which may again transition from red to blue through white or other colorspectrum. For example, if the arrays of LEDs have five individual LEDsas shown, the LEDs of the array of LEDs may transition from left toright as follows: red, yellow, white, green, and blue, wherein the CCTlevel associated with each LEDs transitions from the minimum CCT levelfor red to the maximum CCT level for blue. Again, the first and secondCCT buttons 144 and 146 need not be integrated with the first and secondCCT LEDs 136 and 142. Further, certain buttons on the wall controller126 may support multiple functions and modes.

Notably, the first and second CCT LEDs 136 and 142 in the embodiments ofFIGS. 21 and 22 may also be used to simply set a current CCT level forone or more associated lighting fixtures 10 by the user. In one mode,the user may set the maximum and minimum CCT levels for the maximum andminimum dimming levels. In another mode, the user may be able to changeand set a fixed CCT level, regardless of dimming level or changes todimming level.

Again, in any of the above embodiments, the primary control may beallocated to either the wall controller 126 or a lighting fixture 10. Ifcontrol resides primarily in the wall controller 126, the user inputsmay be processed alone or in conjunction with other criteria todetermine how to instruct the lighting fixture 10 to operate. If controlresides primarily in the lighting fixture 10, the user inputs arerelayed to the lighting fixture 10, which will determine how to respond.The lighting fixture 10 may also determine how the wall controller 126should respond and provide instructions to respond accordingly. Forexample, if the wall controller 126 can set an LED on the wallcontroller 126 to emit light at a color or intensity that is indicativeof a current CCT or CCT setting, the lighting fixture 10 may instructthe wall controller 126 to emit light of a specific color based on thecurrent state of the lighting fixture 10.

An exemplary block diagram of the wall controller 126 is shown in FIG.23. The wall controller 126 includes control circuitry 148, which isassociated with memory 150 and configured to run the requisite softwareor firmware necessary to implement the functionality described herein.The control circuitry is associated with a user input interface (I/F)152 and a user output interface (I/F) 154. As noted above, the userinput interface 152 may include the various switches, rotary knobs,sliders, and buttons, such as the on-off button 130, dimming button 132,CCT button 134, first CCT button 144, second CCT button 146, and thelike. The user input interface 152 may be arranged in various groups ofswitches, knobs, sliders, and buttons. The user input interface couldalso be a touch screen interface. The user output interface 154 mayinclude the CCT LEDs 136, 142, other LEDs or indicators, a display, orthe like. The display could form part of the touch screen interface.

The control circuitry 148 is also associated with one or both of awireless communication interface 156 and a wired communication interface158. The wireless communication interface 156 is configured tofacilitate wireless communication directly with one or more associatedlighting fixtures 10, a wireless network that includes the associatedlighting fixtures, or the like. Virtually any type of wirelesscommunication technique may be used including Bluetooth, wireless localarea network (WLAN), and the like. Even infrared, acoustic, and opticalcommunication techniques are possible.

In one embodiment, the wireless communication interface 156 is capableof communicating with the communication module 32 of at least one of theassociated lighting fixtures 10. Each lighting fixture 10 may beconfigured to relay messages between other lighting fixtures 10 and thewall controller 126. The lighting fixtures 10 may also be able toreceive a signal from a wall controller 126 and then control otherlighting fixtures 10 based on that instruction. The wired communicationinterface 158 is designed to be directly wired to at least one of theassociated lighting fixtures 10 and send the control signals over thewired connection.

In operation, the control circuitry 148 may receive user input via theuser input interface 152 or information from the lighting fixtures 10and commissioning tool 36. Based on this input or information, thecontrol circuitry 148 can provide user feedback to the user via the useroutput interface 154, send instructions via an appropriate signal to oneor more associated lighting fixtures 10 via the wireless or wiredcommunication interfaces 156, 158, or both. For example, the controlcircuitry 148 can receive on-off commands, dimming levels, CCT settings,maximum or minimum CCT levels, and the like from the user inputinterface 152 as described above and provide output to the user via theuser output interface 154 and the associated lighting fixtures 10. Theoutput provided to the user may be controlling the color or intensity ofthe first and second CCT LEDs 136, 142. The signal provided to thelighting fixtures 10 may include the user input or instructions to turnon, turn off, set or transition to a certain CCT level, set ortransition to a certain dimming level, and the like.

The wall controller 126 may also include various sensors, such as anoccupancy sensor 160 and an ambient light sensor 162. The controlcircuitry 148 may simply relay the sensor outputs of the occupancysensor 160 and the ambient light sensor 162 to the associated lightfixtures 10 or use the sensor outputs to help determine how to controlthe associated light fixtures 10. For example, ambient light levels andoccupancy information may affect whether the wall controller 126 willturn on or off the associated lighting fixtures 10 as well as whatdimming levels and CCT levels to set based on a desired lightingschedule that is implemented in the wall controller 126, assuming thelighting schedule is not controlled by one of the associated lightingfixtures 10. The time of day, day of week, and date may also impact howthe associated lighting fixtures 10 are controlled in general as well asin conjunction with the sensor outputs, user inputs, and the like.

With reference to FIGS. 24 and 25, an exemplary commissioning tool 36 isillustrated. The commissioning tool 36 includes a housing 164 in which adisplay 166 and user buttons 168 are integrated. The display 166 may beconfigured as a touch screen device, wherein all or a portion of theuser buttons 168 or like input mechanisms are effectively integratedwith the display 166. A power and communication port 170 is shown on oneend of the housing 164 in FIG. 24, and a light output port 172 is shownon the opposite end of the housing 164 in FIG. 25. The light output port172 is the mechanism from which the a light beam may be projected. Theelectronics of the commissioning tool 36 are described below.

With reference to FIG. 26, electronics for the commissioning tool 36 mayinclude control circuitry 174 that is associated with a wirelesscommunication interface 176, a wired communication interface 178, alight projection system 180, location detection system 182, display 166,and the user buttons 168. The control circuitry 174 is based on one ormore application-specific integrated circuits, microprocessors,microcontrollers, or like hardware, which are associated with sufficientmemory to run the firmware, hardware, and software necessary to impartthe functionality described herein.

Everything may be powered by a power supply 184, which may include abattery and any necessary DC-DC conversion circuitry to convert thebattery voltage to the desired voltages for powering the variouselectronics. The display 166 and user buttons 168 provide a userinterface that displays information to the user and allows a user toinput information to the commissioning tool 36.

The wireless communication interface 176 facilitates wirelesscommunications with the lighting fixtures 10 directly or indirectly viaan appropriate wireless network. The wireless communication interface176 may also be used to facilitate wireless communications with apersonal computer, wireless network (WLAN), and the like. Virtually anycommunication standard may be employed to facilitate suchcommunications, including Bluetooth, IEEE 802.11 (wireless LAN), nearfield, cellular, and the like wireless communication standards. Thewired communication interface 178 may be used to communicate with apersonal computer, wired network (LAN), lighting fixtures 10, and thelike. The light projection system 180 may take various forms, such as alaser diode or light emitting diode that is capable of emitting a lightsignal that can be received by the lighting fixtures 10 via the ambientlight sensor S_(A) or other receiver mechanism.

For example, the light projection system 180 may be used to transmit afocused light signal that can be directed at and recognized by aspecific lighting fixture 10 to select the lighting fixture 10. Theselected lighting fixture 10 and the commissioning tool 36 can thenstart communicating with each other via the wireless communicationinterface 176 to exchange information and allow the instructions anddata to be uploaded to the lighting fixture 10. In other embodiments,the commissioning tool 36 may query the addresses of the lightingfixtures 10 and systematically instruct the lighting fixtures 10 tocontrol their light outputs to help identify each lighting fixture 10.Once the right lighting fixture 10 is identified, the commissioning tool36 can beginning configuring or controlling the lighting fixture 10.

The commissioning tool 36 may be used to set any parameter in andcontrol virtually any aspect of the lighting fixtures 10 and the wallcontrollers 126. For example, the commission tool can be used to set CCTlevels, CCT fade rates, dimming rates, dimming levels, maximum andminimum CCT levels and dimming levels, and the like. The commissioningtool 36 can be used to provide all of the control that was describedabove for the wall controllers 126, and thus act as a remote control forthe lighting fixtures 10, as well as programming tool for morecomplicated scheduling, parameter setting, and the like. Afterinstallation of a lighting fixture 10, the commissioning tool 36 can beused to set or change the CCT level for the lighting fixture 10 invirtually any increment for any light output level, a maximum dimminglevel, minimum dimming level, and the like as well as set the maximumand minimum dimming levels for the lighting fixtures 10. Thecommissioning tool 36 can also be used to program the wall controllers126 to set parameters and perform various tasks in response to virtuallyany input, including user input, time of day, day of week, date, sensordata, and the like.

All of the control circuitry discussed herein for the lighting fixtures10, wall controllers 126, and commissioning tool 36 is defined ashardware based and configured to run software, firmware, and the like toimplement the described functionality. These systems are able to keeptrack of the time of day and day of week to implement scheduledprogramming.

Those skilled in the art will recognize improvements and modificationsto the embodiments of the present disclosure. For example, thetechniques disclosed herein may be employed in a lighting fixture thatuses waveguide technology, such as that provided in InternationalApplication No. PCT/US14/13937, filed Jan. 30, 2014, entitled “OpticalWaveguide Bodies and Luminaires Utilizing Same,” which claims thebenefit of U.S. Provisional Patent Application No. 61/922,017, filedDec. 30, 2013, entitled “Optical Waveguide Bodies and LuminairesUtilizing Same,” and which is a continuation-in-part of U.S. patentapplication Ser. No. 13/842,521, filed Mar. 15, 2013, entitled “OpticalWaveguides,” the disclosures of which are incorporated herein in theirentirety.

All such improvements and modifications are considered within the scopeof the concepts disclosed herein and the claims that follow.

What is claimed is:
 1. A lighting fixture comprising: at least two LEDstrings wherein each string of the at least two LED strings emits lightat a different color point; a driver module configured to: store acurrent model for each string wherein each current model effectivelydefines current as a function of Correlated Color Temperature (CCT) overa CCT range; determine a desired CCT; and generate a current for eachstring based on the desired CCT using a corresponding current model,such that the light from each string mixes to form white light with acolor point that falls along a black body locus at the desired CCT. 2.The lighting fixture of claim 1 wherein the current model for eachstring further defines the current as a function of temperature and thedriver module is further configured to receive a temperature andgenerate the current for each string based on the desired CCT and thetemperature using the corresponding current model, such that the lightfrom each string mixes to form the white light with a color point thatfalls along the black body locus at the desired CCT, regardless of thetemperature.
 3. The lighting fixture of claim 1 wherein the currentmodel for each string further defines the current as a function ofdimming level for the white light and the driver module is furtherconfigured to receive a desired dimming level and generate the currentfor each string based on the desired CCT and the desired dimming levelusing the corresponding current model, such that the light from eachstring mixes to form the white light with a color point that falls alongthe black body locus at the desired CCT and with the desired dimminglevel.
 4. The lighting fixture of claim 3 wherein the driver module isfurther configured to associate a first dimming level with a first CCTand a second dimming level with a second CCT, such that as the dimminglevel progresses from the first dimming level to the second dimminglevel, the desired CCT will proportionately progress from the first CCTto the second CCT along the black body locus, and vice versa.
 5. Thelighting fixture of claim 1 wherein the driver module is furtherconfigured to receive a tuning offset for each current model and adjusteach current model based on a corresponding tuning offset.
 6. Thelighting fixture of claim 5 wherein each tuning offset is an adjustmentcorresponding to a single point calibration.
 7. The lighting fixture ofclaim 1 wherein the current model for each string further defines thecurrent as a function of temperature and dimming level, the drivermodule further configured to receive a temperature and a desired dimminglevel and generate the current for each string based on the desired CCT,the temperature, and the desired dimming level using the correspondingcurrent model, such that the light from each string mixes to form thewhite light with a color point that falls along the black body locus atthe desired CCT and with the desired dimming level, regardless of thetemperature.
 8. The lighting fixture of claim 7 wherein the drivermodule is further configured to receive a tuning offset for each currentmodel and adjust each current model based on a corresponding tuningoffset.
 9. The lighting fixture of claim 8 wherein each tuning offset isan adjustment corresponding to a single point calibration.
 10. Thelighting fixture of claim 1 wherein a CCT range is at least 3000 K to5000 K.
 11. The lighting fixture of claim 1 wherein a CCT range is atleast 2700 K to 5700 K.
 12. The lighting fixture of claim 1 wherein aCCT range is at least 3000 K to 4000 K.
 13. The lighting fixture ofclaim 1 wherein the desired CCT is received from another lightingfixture.
 14. The lighting fixture of claim 1 wherein the desired CCT isreceived from a commissioning tool.
 15. The lighting fixture of claim 1wherein the desired CCT is received from a wall controller.
 16. Thelighting fixture of claim 1 wherein the desired CCT is selected based onone of time of day, day of week, and date by the driver module.
 17. Thelighting fixture of claim 1 wherein the at least two LED stringscomprises a string of wavelength converted LEDs of essentially a firstcolor with a first color point on a CIE 1976 chromaticity diagram; astring of wavelength converted LEDs of essentially a second color with asecond color point on the CIE 1976 chromaticity diagram; and a string ofLEDs of essentially a third color with a third color point on the CIE1976 chromaticity diagram such that a difference in v′ of the firstcolor point and the second color point is greater than 0.033.
 18. Thelighting fixture of claim 17 wherein the difference in v′ of the firstcolor point and the second color point is greater than 0.0400 and lessthan 0.1500.
 19. The lighting fixture of claim 17 wherein the differencein v′ of the first color point and the second color point is greaterthan 0.0500 and less than 0.1500.
 20. The lighting fixture of claim 17wherein the driver module is configured to provide a first current tothe string of wavelength converted LEDs of essentially the first color;a second current to the string of wavelength converted LEDs ofessentially the second color; and a third current to the string of LEDsof essentially the third color to form the white light with a colorpoint that falls along the black body locus.
 21. The lighting fixture ofclaim 20 wherein the driver module is further configured to variablycontrol ratios of the first, second, and third currents such that acorrelated color temperature for the white light is adjustable along theblack body locus from about 3000 K to about 4000 K.
 22. The lightingfixture of claim 21 wherein the string of wavelength converted LEDs ofessentially the first color consists essentially of blue-shifted LEDs,the string of wavelength converted LEDs of essentially the second colorconsists essentially of blue-shifted LEDs, and the string of LEDs ofessentially the third color consists essentially of red LEDs.
 23. Thelighting fixture of claim 1 wherein the at least two LED stringscomprises a string of LEDs of essentially a first color with a firstcolor point on a CIE 1976 chromaticity diagram; a string of LEDs ofessentially a second color with a second color point on the CIE 1976chromaticity diagram; and a string of LEDs of essentially a third colorwith a third color point on the CIE 1976 chromaticity diagram such thata difference in v′ of the first color point and the second color pointis greater than 0.033.
 24. The lighting fixture of claim 23 wherein thedriver module is configured to provide a first current to the string ofLEDs of essentially the first color; a second current to the string ofLEDs of essentially the second color; and a third current to the stringof LEDs of essentially the third color to form the white light with acolor point that falls along the black body locus.
 25. The lightingfixture of claim 24 wherein the driver module is further configured tovariably control ratios of the first, second, and third currents suchthat a correlated color temperature for the white light is adjustablealong the black body locus from about 3000 K to about 4000 K.
 26. Thelighting fixture of claim 1 wherein the driver module is furtherconfigured to: receive a new CCT generate a new current for each stringbased on the new CCT using a corresponding current model, such that thelight from each string mixes to form the white light with a color pointthat falls along the black body locus at the new CCT.
 27. The lightingfixture of claim 26 wherein the driver module is further configured toreceive a fade rate, wherein the driver module will generate a currentfor each string to cause the white light to transition from the desiredCCT to the new CCT along the black body locus at the fade rate.
 28. Alighting fixture comprising: at least two LED strings, wherein eachstring of the at least two LED strings emits light; a driver moduleconfigured to: store a current model for each string wherein eachcurrent model effectively defines current as a function of CorrelatedColor Temperature (CCT) over a CCT range; determine a desired CCT; andgenerate a current for each string based on the desired CCT using acorresponding current model, such that the light from each string mixesto form white light with a color point that falls along a black bodylocus at the desired CCT.
 29. The lighting fixture of claim 28 whereinthe white light has a color rendering index level above
 90. 30. Thelighting fixture of claim 29 wherein the CCT range is at least 3000 K to4000 K.
 31. The lighting fixture of claim 30 wherein the current modelfor each string further defines the current as a function of temperatureand dimming level, the driver module further configured to receive atemperature and a desired dimming level and generate the current foreach string based on the desired CCT, the temperature, and the desireddimming level using the corresponding current model, such that the lightfrom each string mixes to form the white light with a color point thatfalls along the black body locus at the desired CCT and with the desireddimming level, regardless of the temperature.
 32. The lighting fixtureof claim 31 wherein the driver module is further configured to receive atuning offset for each current model and adjust each current model basedon a corresponding tuning offset.